Electronic paper

ABSTRACT

An object of the present invention is to increase the resistance of electronic paper to external stress. The resistance to external stress is increased by providing an element formation layer, which includes an integrated circuit portion, a first electrode, a second electrode, and a charged particle-containing layer, between a first insulating film including a first structure body in which a first fibrous body is impregnated with a first organic resin, and a second insulating film including a second structure body in which a second fibrous body is impregnated with a second organic resin.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic paper and a method formanufacturing the same, and particularly relates to flexible electronicpaper and a method for manufacturing the same.

2. Description of the Related Art

In recent years, display devices such as liquid crystal display devicesand EL display devices have been extensively researched, and as one ofthe display devices capable of operating with low power consumption,electronic paper has attracted attention. The electronic paper has theadvantage that it consumes less power and it can hold images even afterbeing turned off, therefore, it has been expected to be applied toe-book readers or posters.

Various kinds of electronic paper using various methods have beenproposed. Like liquid crystal display devices and the like, activematrix electronic paper using a transistor as a switching element of apixel has been proposed (for example, see Patent Document 1).

-   [Patent Document]-   [Patent Document 1] Japanese Published Patent Application No.    2002-169190

When electronic paper is used as an e-book reader, it is frequentlytouched with hands. Accordingly, elements included in the electronicpaper, such as transistors, need to have mechanical strength andresistance to static electricity. When electronic paper is attached to aroof or a window of a building to be used as a poster or the like, theelectronic paper needs to have high weather resistance, durability, andthe like. Thus, in order to obtain highly reliable electronic paper, itis necessary to increase the resistance of the electronic paper toexternally applied force (hereinafter, also referred to as externalstress).

One object of an embodiment of the present invention is to increase theresistance of electronic paper to external stress.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, an elementformation layer is provided between a first insulating film including afirst structure body in which a first fibrous body is impregnated with afirst organic resin, and a second insulating film including a secondstructure body in which a second fibrous body is impregnated with asecond organic resin, whereby the resistance to external stress can beincreased. Note that the external stress includes all the kinds ofstress that may adversely affect electronic paper, such as modificationsuch as bending, mechanical stress such as locally applied pressure(pressing force), electrical stress such as static electricity, physicalstress such as wind, rain, or dust.

One embodiment of the present invention includes a first insulating filmand a second insulating film facing each other, and an element formationlayer provided between the first insulating film and the secondinsulating film. The element formation layer includes an integratedcircuit portion, a first electrode electrically connected to theintegrated circuit portion, a second electrode facing the firstelectrode, and a charged particle-containing layer provided between thefirst electrode and the second electrode. The first insulating filmincludes a first structure body in which a first fibrous body isimpregnated with a first organic resin, and the second insulating filmincludes a second structure body in which a second fibrous body isimpregnated with a second organic resin. The first organic resin and thesecond organic resin are bonded to each other at the edges of the firstinsulating film and the second insulating film.

One embodiment of the present invention includes a first insulating filmand a second insulating film facing each other, and an element formationlayer provided between the first insulating film and the secondinsulating film. The element formation layer includes an integratedcircuit portion, a first electrode electrically connected to theintegrated circuit portion, a second electrode facing the firstelectrode, and a charged particle-containing layer provided between thefirst electrode and the second electrode. The first insulating filmincludes a first structure body in which a first fibrous body isimpregnated with a first organic resin, and a first protective filmhaving a modulus of elasticity lower than that of the first structurebody. The second insulating film includes a second structure body inwhich a second fibrous body is impregnated with a second organic resin,and a second protective film having a modulus of elasticity lower thanthat of the second structure body. The first organic resin and thesecond organic resin are bonded to each other at the edges of the firstinsulating film and the second insulating film.

According to one embodiment of the present invention, an elementformation layer is provided between a first insulating film having afirst structure body in which a first fibrous body is impregnated with afirst organic resin, and a second insulating film having a secondstructure body in which a second fibrous body is impregnated with asecond organic resin, whereby the resistance of electronic paper toexternal stress can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are diagrams each illustrating an example of electronicpaper;

FIG. 2 is a diagram illustrating an example of electronic paper;

FIGS. 3A and 3B are diagrams each illustrating an example of electronicpaper;

FIGS. 4A and 4B are diagrams each illustrating an example of a methodfor manufacturing electronic paper;

FIGS. 5A to 5D are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 6A to 6E are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 7A to 7C are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 8A and 8B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 9A and 9B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 10A to 10D are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 11A to 11C are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 12A and 12B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 13A and 13B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 14A to 14E are diagrams illustrating an example of a method formanufacturing electronic paper;

FIG. 15 is a diagram illustrating an example of a method formanufacturing electronic paper;

FIGS. 16A to 16D are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 17A and 17B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 18A and 18B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 19A and 19B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 20A and 20B are diagrams illustrating an example of a method formanufacturing electronic paper;

FIGS. 21A and 21B are diagrams illustrating an example of electronicpaper;

FIGS. 22A and 22B are views each illustrating an example of theapplication of electronic paper;

FIGS. 23A and 23B are views illustrating an example of a structure bodyin which a fibrous body is impregnated with an organic resin; and

FIG. 24 is a view illustrating an example of a structure body in which afibrous body is impregnated with an organic resin.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail withreference to drawings. Note that the present invention is not limited tothe description below, and it is apparent to those skilled in the artthat modes and details can be modified in various ways without departingfrom the spirit and scope of the present invention. Accordingly, thepresent invention should not be construed as being limited to thedescription of the embodiments given below. Note that in the structuresof the present invention described below, like portions or portionshaving a similar function are denoted by like reference numerals, andthe description thereof is omitted.

Embodiment 1

In this embodiment, an example of electronic paper will be describedwith reference to drawings.

Electronic paper shown in this embodiment includes a first insulatingfilm 51 and a second insulating film 52 facing each other, and anelement formation layer 53 provided between the first insulating film 51and the second insulating film 52. The first insulating film 51 includesa first structure body in which a fibrous body 71 a is impregnated witha first organic resin 71 b, and the second insulating film 52 includes asecond structure body in which a fibrous body 72 a is impregnated with asecond organic resin 72 b. In a region where the element formation layer53 is not provided (for example, at the edges of the first insulatingfilm 51 and the second insulating film 52), the first organic resin 71 bis bonded to the second organic resin 72 b (see FIG. 1A).

FIGS. 1A and 1B show the case where the first insulating film 51includes only the first structure body (the first structure bodycorresponds to the first insulating film 51); however, the firstinsulating film 51 may also include another insulating layer stacked onthe first structure body. The same applies to the second insulating film52. The first insulating film 51 and the second insulating film 52 aremade of a flexible insulating material.

The element formation layer 53 includes: an integrated circuit portion54 having elements such as transistors and capacitors; first electrodes55 electrically connected to the elements of the integrated circuitportion 54; a second electrode 57 facing the first electrodes 55; and acharged particle-containing layer 56 provided between the firstelectrodes 55 and the second electrode 57.

FIG. 1A illustrates an active matrix structure in which the integratedcircuit portion 54 includes transistors 61 and the transistors 61 areelectrically connected to the first electrodes 55. It is needless to saythat the structure of the electronic paper shown in this embodiment isnot limited to this structure, and a transistor 65 constituting a scanline driver circuit, a signal line driver circuit, or a memory circuitmay be provided in the same process as the transistors 61 constitutingthe pixels (see FIG. 1B).

The integrated circuit portion 54 may include an antenna so that datacan be wirelessly communicated with the outside. In that case, data suchas images to be displayed can be received from the outside through theantenna provided in the integrated circuit portion 54.

Note that there is no particular limitation on the structure of thetransistors in FIGS. 1A and 1B, and it is possible to use a variety ofstructures such as a single-drain structure, an LDD (lightly-dopeddrain) structure, or a gate-overlap drain structure. Here, a thin filmtransistor using a crystalline semiconductor is shown which has an LDDstructure in which low-concentration impurity regions are provided usinginsulating layers (also referred to as sidewalls) touching the sides ofa gate electrode; however, the present invention is not limited to sucha transistor. For example, a thin film transistor using an amorphoussemiconductor or an organic transistor may also be used.

As another structure of the transistors, it is also possible to use amultigate structure in which transistors having substantially the samegate voltage are connected in series, a dual gate structure in which asemiconductor layer is interposed between gate electrodes, or the like.Alternatively, a diode, an MIM (metal-insulator-metal), MEMS (microelectro mechanical systems), or the like can be used instead of thetransistors if it serves as a switching element of a pixel of electronicpaper.

The charged particle-containing layer 56 contains charged particles. Thecharged particles move under the influence of an electric field appliedbetween the first electrodes 55 and the second electrode 57, wherebyimages can be displayed. The material of the charged particle-containinglayer 56 may be selected as appropriate depending on the system used forelectronic paper (the microcapsule electrophoresis system, thehorizontal type electrophoresis system, the vertical electrophoresissystem, a system using a twisting ball, a system using a charged toner,a system using Electronic Liquid Powder (trademark), or the like).

For example, as the charged particle-containing layer 56, it is possibleto use a microcapsule containing positively-charged particles of onecolor and negatively-charged particles of another color.

As the fibrous bodies 71 a and 72 a provided over and under the elementformation layer 53, high-strength fibers of an organic compound or aninorganic compound can be used. As typical examples of the high-strengthfibers, there are a polyvinyl alcohol fiber, a polyester fiber, apolyamide fiber, a polyethylene fiber, an aramid fiber, apolyparaphenylene benzobisoxazole fiber, a glass fiber, a carbon fiber,and the like. As the glass fiber, a glass fiber using E glass, S glass,D glass, Q glass, or the like can be used. Note that the fibrous bodies71 a and 72 a may be formed of one kind of the above high-strengthfibers or plural kinds of the above high-strength fibers. The fibrousbody is not necessarily provided over and under the element formationlayer 53, and may be provided either over or under the element formationlayer 53.

The fibrous bodies 71 a and 72 a may be a woven fabric that is wovenfrom bundles of fibers (single yarns) (hereinafter referred to asbundles of yarns) used for warp yarns and weft yarns, or a nonwovenfabric obtained by stacking bundles of plural kinds of fibers randomlyor regularly. In the case of a woven fabric, a plain-woven fabric, atwilled fabric, a satin-woven fabric, or the like can be used asappropriate.

The bundle of yarns may have a circular shape or an elliptical shape incross section. The bundle of fiber yarns may be subjected to fiberopening with a high-pressure water stream, high-frequency vibrationusing liquid as a medium, continuous ultrasonic vibration, pressing witha roller, or the like. The bundle of fiber yarns, which has beensubjected to fiber opening, has a large width and has an ellipticalshape or a flat shape in cross section, which allows the number ofsingle yarns in the thickness direction to be reduced. Furthermore, withthe use of a loosely twisted yarn as the bundle of fiber yarns, thebundle of yarns is easily flattened and has an elliptical shape or aflat shape in cross section. By using such a bundle of yarns having anelliptical shape or a flat shape in cross section, the thickness of eachof the fibrous bodies 71 a and 72 a can be reduced, and thin electronicpaper can be manufactured.

The diameter of the bundle of fiber yarns is 4 μm to 400 μm, andpreferably 4 μm to 200 μm.

FIGS. 4A and 4B are top views of a woven fabric that is woven frombundles of fiber yarns used for warp yarns and weft yarns, which is usedas the fibrous bodies 71 a and 72 a.

In FIG. 4A, each of the fibrous bodies 71 a and 72 a is woven fromregularly-spaced warp yarns 70 a and regularly-spaced weft yarns 70 b.Such a fibrous body has regions (referred to as basket holes 70 c) whereneither the warp yarns 70 a nor the weft yarns 70 b exist. These regionsare impregnated with an organic resin.

As illustrated in FIG. 4B, each of the fibrous bodies 71 a and 72 a mayhave a high density of the warp yarns 70 a and the weft yarns 70 b andthe proportion of the basket holes 70 c may be low. Typically, the sizeof each of the basket holes 70 c is preferably smaller than that of thearea locally pressed. Typically, it is preferable that each of thebasket holes 70 c have a rectangular shape with a side length of 0.01 mmto 0.2 mm. If each of the basket holes 70 c of the fibrous bodies 71 aand 72 a has such a small area, even when pressure is applied by amember with a sharp tip (typically, a writing instrument such as a penor a pencil), the pressure can be absorbed by the entire fibrous bodies71 a and 72 a.

FIGS. 23A and 23B and FIG. 24 illustrate an example in which a fibrousbody is impregnated with an organic resin. Note that FIG. 23A is a SEMimage (magnified 1000 times) of a cross-section of a sample actuallymanufactured, and FIG. 23B is a schematic view of FIG. 23A. FIG. 24shows an image (magnified 20 times) of the cross-section of the sampleactually manufactured, which was observed by an optical microscope.

FIGS. 23A and 23B shows the case in which the first structure body 51 inwhich the fibrous body 71 a is impregnated with the organic resin 71 band the second structure body 52 in which the fibrous body 72 a isimpregnated with the organic resin 72 b are provided with a transistorportion 50 interposed therebetween. Although the cross-sectional viewsof FIGS. 23A and 23B show only one of the warp yarns and the weft yarnsas the fibrous body 71 a and the fibrous body 72 a, the other fibrousbody intersecting the one of the warp yarns and the weft yarns existsdepending on the direction of the cross-section observed.

The cross-sectional view of FIG. 24 shows that warp yarns and weft yarnseach including a bundle of fibers intersect each other.

As described above, the fibrous bodies are woven into fabric form sothat the warp yarns and the weft yarns cross each other, and the wovenfabric is impregnated with an organic resin. Accordingly, expansion andcontraction of the woven fabric in the direction of the surface of thefabric can be suppressed by the fibrous bodies, and flexibility in thedirection perpendicular to the surface direction can be obtained.

As illustrated in FIGS. 4A and 4B, the fibrous bodies are woven intofabric form so that the warp yarns and the weft yarns cross each other,and the woven fabric is impregnated with an organic resin. Accordingly,expansion and contraction of the woven fabric in the direction of thesurface of the fabric can be suppressed by the fibrous bodies, andflexibility in the direction perpendicular to the surface direction canbe obtained.

In order to enhance the permeability of an organic resin in the bundlesof fiber yarns, the fibers may be subjected to surface treatment. Forexample, corona discharge or plasma discharge may be performed toactivate the surface of the fibers. Alternatively, surface treatment maybe performed using a silane coupling agent or a titanate coupling agent.

The first organic resin 71 b and the second organic resin 72 b, withwhich the fibrous bodies 71 a and 72 a are impregnated, respectively,and the element formation layer 53 is sealed, can be made of athermosetting resin such as an epoxy resin, an unsaturated polyesterresin, a polyimide resin, a bismaleimide-triazine resin, or a cyanateresin. Alternatively, a thermoplastic resin such as a polyphenyleneoxide resin, a polyetherimide resin, or a fluorine resin may be used.Further, plural kinds of the aforementioned thermosetting resins andthermoplastic resins may also be used as the organic resins 71 b and 72b. By using the aforementioned organic resins, the fibrous bodies 71 aand 72 a can be firmly bonded to the element formation layer by heattreatment. Note that the higher the glass transition temperature of thefirst organic resin 71 b and the second organic resin 72 b is, the lessthe organic resins are damaged by locally applied force, which ispreferable.

The thickness of each of the first structure body and the secondstructure body is preferably 10 μm to 100 μm, and more preferably 10 μmto 30 μm. By using the structure body with such a thickness, thinelectronic paper that can be bent can be manufactured.

Highly thermally-conductive filler may be dispersed in the first organicresin 71 b and the second organic resin 72 b, or the bundles of fiberyarns. As the highly thermally-conductive filler, aluminum nitride,boron nitride, silicon nitride, or alumina can be used. Alternatively,metal particles such as silver or copper particles may be used. When thehighly thermally-conductive filler is included in the organic resins orthe bundles of fiber yarns, heat generated in the element formationlayer 53 can be easily released to the outside. Accordingly, thermalstorage in the element formation layer 53 can be suppressed and thusdamage to the electronic paper and display defects can be reduced.

The effect of the electronic paper shown in this embodiment will bedescribed with reference to FIGS. 5A to 5D.

As illustrated in FIG. 5A, conventional electronic paper has a structurein which an element formation layer 40 is sealed with insulating films41 a and 41 b. When external stress (pressure 42) is locally applied tosuch electronic paper, the element formation layer 40 and the insulatingfilms 41 a and 41 b each stretch as illustrated in FIG. 5B, the pressedportion is curved with a small radius of curvature. As a result,semiconductor elements, wirings, and the like constituting the elementformation layer 40 are cracked and the electronic paper is broken.

However, in the electronic paper shown in this embodiment, a fibrousbody having a high tensile modulus of elasticity or a high Young'smodulus is firmly bonded over and under the element formation layer 53with an organic resin as illustrated in FIG. 5C. Therefore, even whenthe pressure 42 such as point pressure or linear pressure is locallyapplied as illustrated in FIG. 5D, high-strength fibers do not stretchand the pressure is dispersed throughout the fibers, so that the entireelectronic paper is curved. Thus, even when pressure is locally applied,the electronic paper is curved with a large radius of curvature;therefore, semiconductor elements, wirings, and the like constitutingthe element formation layer 53 are not cracked and damage to theelectronic paper can be reduced.

In addition, when the first organic resin 71 b and the second organicresin 72 b are directly bonded to each other as shown in thisembodiment, the adhesion between the first insulating film 51 and thesecond insulating film 52 can be improved, moisture or the like can beprevented from entering from the bonding surface, and the separation ofthe first insulating film 51 and the second insulating film 52 can besuppressed.

It is preferable that the element formation layer 53 be placed in themiddle of the first insulating film 51 and the second insulating film 52(i.e., the first insulating film 51 and the second insulating film 52have substantially the same thickness). In that case, the firstinsulating film 51 (the first structure body) and the second insulatingfilm 52 (the second structure body) are symmetrically disposed withrespect to the element formation layer 53. Accordingly, the forceapplied to the element formation layer 53 when the electronic paper iscurved or the like can be evenly dispersed, and damage to the elementformation layer 53 due to bending or warping of the electronic paper canbe reduced.

Furthermore, in the electronic paper shown in this embodiment, a barrierlayer is preferably provided between the element formation layer 53 andthe first insulating film 51, and between the element formation layer 53and the second insulating film 52. For example, as illustrated in FIGS.1A and 1B, a first barrier layer 62 and a second barrier layer 63 can beprovided to cover the integrated circuit portion 54.

Here, the integrated circuit portion 54 is provided over the firstbarrier layer 62, the second barrier layer 63 is provided to cover thefirst electrode 55, and the first barrier layer 62 and the secondbarrier layer 63 touch each other at their edges, whereby the integratedcircuit portion 54 is surrounded by the barrier layers. With such astructure, impurities such as moisture or alkali metal can be preventedfrom entering and degradation of elements such as transistors includedin the integrated circuit portion 54 can be reduced. This structure isparticularly effective in the case where an organic material is used forthe elements of the integrated circuit portion 54 (in the case whereorganic transistors are provided in the integrated circuit portion 54).

Note that the first barrier layer 62 and the second barrier layer 63 maybe provided to surround the entire element formation layer 53. In thatcase, the second barrier layer 63 may be provided over the secondelectrode 57.

As the barrier layers 62 and 63, a nitrogen-containing layer (siliconnitride, silicon nitride oxide, silicon oxynitride, or the like) can beused.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 2

In this embodiment, an example of a method for manufacturing theelectronic paper shown in Embodiment 1 will be described with referenceto drawings.

First, a separation layer 102 is formed on a surface of a substrate 100,and then, an insulating layer 104 is formed (see FIG. 6A). Theseparation layer 102 and the insulating layer 104 can be formedcontinuously, which prevents impurities from entering because thesubstrate 100 is not exposed to the atmosphere.

As the substrate 100, a glass substrate, a quartz substrate, a metalsubstrate, a stainless steel substrate, or the like can be used. Forexample, by using a rectangular glass substrate with a side of one meteror more, productivity can be significantly increased.

Note that the separation layer 102 is formed on the entire surface ofthe substrate 100 in this process; however, after the separation layer102 is formed on the entire surface of the substrate 100, the separationlayer 102 may be selectively removed so that the separation layer can beprovided only in a desired region. In addition, although the separationlayer 102 is formed in contact with the substrate 100, an insulatinglayer such as a silicon oxide film, a silicon oxynitride film, a siliconnitride film, or a silicon nitride oxide film may be formed in contactwith the substrate 100 as needed, and the separation layer 102 may beformed in contact with the insulating layer.

The separation layer 102 has a single-layer structure or a multi-layerstructure of a film made of a material such as tungsten (W), molybdenum(Mo), titanium (Ti), tantalum (Ta), niobium (Nb), nickel (Ni), cobalt(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh), palladium(Pd), osmium (Os), iridium (Ir), or silicon (Si). Alternatively, theseparation layer 102 may be made of an alloy containing such an elementas its main component, or a compound containing such an element as itsmain component. Those materials can be formed by sputtering, plasma CVD,coating, printing, or the like to a thickness of 30 nm to 200 nm. Notethat the coating is a deposition method in which a solution isdischarged on an object, and includes, for example, spin coating ordroplet discharging. The droplet discharging is a method in which adroplet of a composition containing fine particles is discharged from asmall hole to form a predetermined pattern.

In the case where the separation layer 102 has a single-layer structure,it is preferable to form a tungsten layer, a molybdenum layer, or alayer containing a mixture of tungsten and molybdenum. Alternatively, alayer containing oxide or oxynitride of tungsten, a layer containingoxide or oxynitride of molybdenum, or a layer containing oxide oroxynitride of a mixture of tungsten and molybdenum may be used. Notethat the mixture of tungsten and molybdenum corresponds to, for example,an alloy of tungsten and molybdenum.

In the case where the separation layer 102 has a multi-layer structure,it is preferable that a metal layer be formed as a first layer and ametal oxide layer be formed as a second layer. Typically, the firstmetal layer is made of tungsten or a mixture of tungsten and molybdenum,and the second layer is made of oxide of tungsten, oxide of a mixture oftungsten and molybdenum, nitride of tungsten, or nitride of a mixture oftungsten and molybdenum.

In the case where the separation layer 102 has a multi-layer structurein which a metal layer is formed as a first layer and a metal oxidelayer is formed as a second layer, the separation layer 102 may beformed in the following manner: a layer containing tungsten is formed asthe metal layer and an insulating layer made of oxide is formedthereover, whereby a layer containing oxide of tungsten is formed as themetal oxide layer at the interface between the tungsten layer and theinsulating layer. Alternatively, the metal oxide layer may be formed byperforming thermal oxidation treatment, oxygen plasma treatment,treatment with a highly oxidizing solution such as ozone water, or thelike on the surface of the metal layer.

The insulating layer 104, which serves as a buffer layer, is provided sothat the separation layer 102 is easily separated in a subsequentseparation step. In addition, the insulating layer 104 can preventsemiconductor elements or wirings from being cracked or damaged in thesubsequent separation step. The insulating layer 104 has a single-layerstructure or a multi-layer structure, and is formed by, for example,sputtering, plasma CVD, coating, or printing using an inorganiccompound. As typical examples of the inorganic compound, there aresilicon oxide, silicon nitride, silicon oxynitride, and silicon nitrideoxide.

By using a nitrogen-containing layer (such as silicon nitride, siliconnitride oxide, or silicon oxynitride) as the insulating layer 104,moisture, impurities, or gas such as oxygen can be prevented fromexternally entering the elements that are formed later. That is, theinsulating layer 104 serves as a barrier layer. The insulating layer 104is preferably formed to a thickness of 10 nm to 1000 nm, and morepreferably a thickness of 100 nm to 700 nm.

Then, a thin film transistor 106 is formed over the insulating layer 104(see FIG. 6B). The thin film transistor 106 includes a semiconductorlayer 108 having at least a source region, a drain region, and a channelformation region, a gate insulating layer 110, and a gate electrode 112.

The semiconductor layer 108 is a non-single-crystal semiconductor layerhaving a thickness of 10 nm to 100 nm, and preferably a thickness of 20nm to 70 nm. As the non-single-crystal semiconductor layer, acrystalline semiconductor layer, an amorphous semiconductor layer, amicrocrystalline semiconductor layer, or the like can be used. As thesemiconductor, silicon, germanium, a silicon—germanium compound, or thelike can be used. It is particularly preferable to use a crystallinesemiconductor that is crystallized by laser light irradiation, heattreatment using rapid thermal annealing (RTA) or an annealing furnace,or a combination of these methods. As the heat treatment, it is possibleto use a crystallization method using a metal element such as nickel,which promotes crystallization of silicon semiconductor.

The gate insulating layer 110 is made of an inorganic insulator such assilicon oxide or silicon oxynitride to a thickness of 5 nm to 200 nm,and preferably 10 nm to 100 nm.

The gate electrode 112 can be made of a metal or a polycrystallinesemiconductor doped with an impurity imparting one conductivity type.When a metal is used, tungsten (W), molybdenum (Mo), titanium (Ti),tantalum (Ta), aluminum (Al), or the like can be used. Alternatively,metal nitride obtained by nitriding a metal can be used. Furtheralternatively, a first layer made of the metal nitride and a secondlayer made of the metal may be stacked as the gate electrode 112. Inthat case, the first layer made of the metal nitride can serve as abarrier metal. That is, the first layer can prevent the metal of thesecond layer from diffusing into the gate insulating layer and thesemiconductor layer under the gate insulating layer. In the case wherethe multi-layer structure is used, the edge of the first layer mayextend beyond the edge of the second layer.

The thin film transistor 106 may have a variety of structures such as asingle-drain structure, an LDD (lightly-doped drain) structure, or agate-overlap drain structure. The thin film transistor 106 shown here isa thin film transistor having an LDD structure in whichlow-concentration impurity regions are provided using insulating layers(also referred to as sidewalls) touching the sides of the gate electrode112. Alternatively, it is possible to use a thin film transistor havinga multigate structure in which transistors having substantially the samegate voltage are connected in series, a dual gate structure in which asemiconductor layer is interposed between gate electrodes, or the like.

Further, a thin film transistor using metal oxide or an organicsemiconductor material for a semiconductor layer may be used as the thinfilm transistor 106. As typical examples of the metal oxide, there arezinc oxide and zinc—gallium—indium oxide.

Next, wirings 118 electrically connected to the source and drain of thethin film transistor 106 are formed, and a first electrode 122electrically connected to one of the wirings 118 is formed (see FIG.6C). The first electrode 122 functions as a pixel electrode.

Here, insulating layers 114 and 116 are formed to cover the thin filmtransistor 106, and the wirings 118 capable of functioning as the sourceand drain electrodes are formed over the insulating layer 116. Then, aninsulating layer 120 is formed over the wirings 118, and the firstelectrode 122 functioning as the pixel electrode is formed over theinsulating layer 120.

The insulating layers 114 and 116 serve as an interlayer insulatinglayer. Each of the insulating layers 114 and 116 has a single-layerstructure or a multi-layer structure, and is made of an inorganicmaterial such as oxide of silicon or nitride of silicon, an organicmaterial such as polyimide, polyamide, benzocyclobutene, acrylic, orepoxy, a siloxane material, or the like. Those materials can be formedby CVD, sputtering, SOG, droplet discharging, screen printing, or thelike. Here, a silicon nitride oxide film can be formed as the firstinsulating layer 114, and a silicon oxynitride film can be formed as thesecond insulating layer 116.

The wirings 118 are preferably formed by a combination of alow-resistance material such as aluminum (Al) and a barrier metal usinga high melting-point material such as titanium (Ti) or molybdenum (Mo).For example, the wirings 118 each have a multi-layer structure oftitanium (Ti) and aluminum (Al) or a multi-layer structure of molybdenum(Mo) and aluminum (Al).

The insulating layer 120 has a single-layer structure or a multi-layerstructure, and is made of an inorganic material such as oxide of siliconor nitride of silicon, an organic material such as polyimide, polyamide,benzocyclobutene, acrylic, or epoxy, a siloxane material, or the like.Those materials can be formed by CVD, sputtering, SOG, dropletdischarging, screen printing, or the like. Here, the insulating layer120 is formed of an epoxy resin by screen printing.

The first electrode 122 can be made of indium tin oxide (ITO) in whichtin oxide is mixed with indium oxide, indium tin silicon oxide (ITSO) inwhich silicon oxide is mixed with indium tin oxide (ITO), indium zincoxide (IZO) in which zinc oxide is mixed with indium oxide, zinc oxide(ZnO), tin oxide (SnO₂), or the like. Alternatively, the first electrode122 may be made of a reflective metal (for example, a material filmcontaining aluminum or silver as its main component, or a multi-layerfilm of such a material film).

Next, the insulating layers on the edge of the substrate 100 are removedby etching or the like, and then, an insulating layer 123 is formed (seeFIG. 6D). Here, at least the insulating layers 114, 116, and 120 areremoved to expose the insulating layer 104. In the case where aplurality of panels are formed over one substrate, the insulating layersare etched on the edge of each region in which each panel is formed, andare divided into separate elements constituting each panel.

The insulating layer 123 serves as a barrier layer, and is preferablyformed to cover at least an integrated circuit portion 125 including thethin film transistor 106. Here, the integrated circuit portion 125 andthe first electrode 122 are surrounded by the insulating layer 104 andthe insulating layer 123 serving as barrier layers.

As the insulating layer 123, a nitrogen-containing layer (siliconnitride, silicon nitride oxide, silicon oxynitride, or the like) can beused.

In order that a layer (hereinafter referred to as an element layer 124)including elements such as the first electrode 122 and the integratedcircuit portion 125 having the thin film transistor 106 and the like iseasily separated from the substrate 100, a groove is preferably formedby laser light irradiation before the element layer 124 is separatedfrom the substrate 100. Here, a groove 128 is formed by irradiating theinsulating layer 104 exposed on the edge of the substrate with laserlight (see FIG. 6E).

Next, as illustrated in FIG. 7A, an adhesive sheet 130 is bonded to theelement layer 124. As the adhesive sheet 130, a sheet that can beseparated by light or heat is used.

The adhesive sheet 130 facilitates the separation, and further reducesthe stress applied to the element layer 124 before and after theseparation and suppresses damage to the elements included in theintegrated circuit portion 125, which results in improved yield.

Next, the element layer 124 is separated from the substrate 100 at theinterface between the separation layer 102 and the insulating layer 104serving as a buffer layer (see FIG. 7B). The separation starts from thegroove 128. The separation may be performed by, for example, applyingmechanical force (pulling by hand or a gripping tool, separating whilerotating a roller, or the like).

Alternatively, a liquid may be dropped into the groove 128 to beinfiltrated into the interface between the separation layer 102 and theinsulating layer 104, so that the element layer 124 can be separatedfrom the separation layer 102. Further alternatively, a fluoride gassuch as NF₃, BrF₃, or ClF₃ may be introduced into the groove 128 and theseparation layer may be removed by etching with the fluoride gas, sothat the element layer 124 can be separated from the substrate having aninsulating surface.

In this embodiment, the element layer 124 is separated from thesubstrate 100 by forming a metal oxide layer as a layer included in theseparation layer 102, which touches the insulating layer 104; however,the present invention is not limited to this separation method. Anotherseparation method may also be used in which a light-transmittingsubstrate is used as the substrate 100, an amorphous silicon layercontaining hydrogen is used as the separation layer 102, and theseparation layer 102 is irradiated with a laser beam from the side ofthe substrate 100 so that hydrogen contained in the amorphous siliconlayer is vaporized, whereby the separation layer 102 can be separatedfrom the substrate 100.

Alternatively, the substrate 100 may be mechanically polished ordissolved in a solution such as HF to be removed. In that case, it isnot necessary to use the separation layer 102.

Next, a first structure body 132 in which a fibrous body 132 a isimpregnated with a first organic resin 132 b is provided on a separationsurface of the element layer 124 (the surface of the insulating layer104 that is exposed by separation) (see FIG. 7C). Such a structure body132 is also called a prepreg.

The prepreg is obtained in such a manner that a fibrous body isimpregnated with a varnish in which a matrix resin is diluted with anorganic solvent, and then the organic solvent is dried and volatilizedso that the matrix resin is semi-cured. The thickness of the structurebody is preferably 10 μm to 100 μm, and more preferably 10 μm to 30 μm.By using the structure body with such a thickness, thin electronic paperthat can be bent can be manufactured.

As the first organic resin 132 b, it is possible to use a thermosettingresin such as an epoxy resin, an unsaturated polyester resin, apolyimide resin, a bismaleimide-triazine resin, or a cyanate resin.Alternatively, a thermoplastic resin such as a polyphenylene oxideresin, a polyetherimide resin, or a fluorine resin may be used as thefirst organic resin 132 b. By using the aforementioned organic resin,the fibrous body can be firmly bonded to the element layer 124 by heattreatment. Note that the higher the glass transition temperature of thefirst organic resin 132 b is, the less the organic resin is damaged bylocally applied force, which is preferable.

The fibrous body 132 a is a woven or nonwoven fabric using high-strengthfibers of an organic compound or an inorganic compound, and provided sothat the warp yarns and the weft yarns cross each other. A high-strengthfiber is specifically a fiber with a high tensile modulus of elasticityor a fiber with a high Young's modulus. As typical examples of thehigh-strength fiber, there are a polyvinyl alcohol fiber, a polyesterfiber, a polyamide fiber, a polyethylene fiber, an aramid fiber, apolyparaphenylene benzobisoxazole fiber, a glass fiber, a carbon fiber,and the like. As the glass fiber, there is a glass fiber using E glass,S glass, D glass, Q glass, or the like. Note that the fibrous body 132 amay be formed of one kind of the above high-strength fibers or pluralkinds of the above high-strength fibers.

Next, the first organic resin 132 b is plasticized or cured bythermocompression bonding of the first structure body 132. For example,in the case where a thermosetting epoxy resin is used as the firstorganic resin 132 b, the first structure body 132 is provided on theseparation surface of the element layer 124, and then subjected tothermocompression bonding, whereby the first organic resin 132 b spreadsevenly on the separation surface of the element layer 124 and is cured.In the case where a thermoplastic resin is used, the first structurebody 132 is provided on the separation surface of the element layer 124and subjected to thermocompression bonding, and then cooled to roomtemperature so that the plasticized organic resin can be cured.

The step of pressure-bonding the first structure body 132 can beperformed under an atmospheric pressure or a reduced pressure.

Next, the adhesive sheet 130 is separated to expose the insulating layer123 (see FIG. 8A).

Next, a charged particle-containing layer 134 is formed over the firstelectrode 122. For example, a binder 138 in which microcapsules 136 aredispersed and fixed is provided over the first electrode 122. Then, asecond electrode 140 is formed over the charged particle-containinglayer 134. Here, by using the binder 138 on which the second electrode140 has been formed in advance, the charged particle-containing layer134 and the second electrode 140 are provided over the first electrode122 with the insulating layer 123 interposed therebetween (see FIG. 8B).

Each of the microcapsules 136 contains a positively-charged particle 136a of one color and a negatively-charged particle 136 b of another color,which are dispersed in a solvent included in the microcapsule. Theparticle 136 a or the particle 136 b move to one side under theinfluence of an electric field applied between the first electrode 122and the second electrode 140 to change the contrast of each pixel,whereby an image can be displayed.

Alternatively, a resin film can be used as the binder 138, and themicrocapsules 136 can be dispersed and fixed in the resin film. Such ause of the binder 138 in which the microcapsules 136 are dispersed andfixed simplifies the manufacturing process.

Instead of the microcapsule, charged polymer fine particles (ElectronicLiquid Powder) and the like may be provided. In that case, apositively-charged polymer fine particle of one color and anegatively-charged polymer fine particle of another color may beprovided between the first electrode 122 and the second electrode 140.

Next, a second structure body 142 in which a fibrous body 142 a isimpregnated with a second organic resin 142 b is provided over thesecond electrode 140 formed over the charged particle-containing layer134 (see FIG. 9A). The second structure body 142 can have a structuresimilar to the first structure body 132.

Then, the second structure body 142 is subjected to thermocompressionbonding, whereby the second organic resin 142 b is bonded to the firstorganic resin 132 b (see FIG. 9B). Here, the first organic resin 132 band the second organic resin 142 b are bonded to each other at the edgesof the first structure body 132 and the second structure body 142 so asto seal the element formation layer. Note that the position in which thefirst organic resin 132 b and the second organic resin 142 b are bondedto each other (in the height direction) can be controlled by thepressure or temperature in bonding.

As shown in this embodiment, by providing the first structure body 132and the second structure body 142 to cover the element formation layer,the resistance of the element formation layer to external stress can beincreased. In addition, when the thickness t₁ of the first organic resin132 b is substantially equal to the thickness t₂ of the second organicresin 142 b (t₁≈t₂) and the first structure body 132 and the secondstructure body 142 are symmetrically disposed with respect to theelement formation layer (the element formation layer is placed in themiddle of the first structure body 132) and the second structure body142, the force applied to the element formation layer when theelectronic paper is curved or the like can be evenly dispersed. As aresult, damage to the element formation layer due to bending or warpingof the electronic paper can be reduced.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 3

In this embodiment, a method for manufacturing the electronic paper,which is different from that shown in the above embodiment, will bedescribed with reference to drawings.

First, the separation layer 102 is formed on a surface of the substrate100 and the insulating layer 104 is continuously formed. Then, a firstelectrode 150 is formed over the insulating layer 104 (see FIG. 10A).The first electrode 150 functions as a pixel electrode.

The first electrode 150 can be made of indium tin oxide (ITO) in whichtin oxide is mixed with indium oxide, indium tin silicon oxide (ITSO) inwhich silicon oxide is mixed with indium tin oxide (ITO), indium zincoxide (IZO) in which zinc oxide is mixed with indium oxide, zinc oxide(ZnO), tin oxide (SnO₂), or the like. Alternatively, the first electrode150 may be made of a reflective metal (for example, a material filmcontaining aluminum or silver as its main component, or a multi-layerfilm of such a material film).

Then, an insulating layer 152 is formed over the first electrode 150,and the thin film transistor 106 is formed over the insulating layer152. Then, the insulating layers 114 and 116 are formed over the thinfilm transistor 106, and the wirings 118 capable of functioning as thesource and drain electrodes are formed over the insulating layer 116(see FIG. 10B).

The thin film transistor 106 may have a variety of structures such as asingle-drain structure, an LDD (lightly-doped drain) structure, or agate-overlap drain structure. The thin film transistor 106 shown herehas a single-drain structure.

One of the wirings 118 is electrically connected to the first electrode150. Here, the wiring 118 is electrically connected to the firstelectrode 150 through a conductive layer 154. The conductive layer 154can be formed at the same time (in the same process) as the gateelectrode of the thin film transistor 106.

Next, the insulating layers on the edge of the substrate 100 are removedby etching or the like, and then, an insulating layer 156 is formed tocover the wirings 118 (see FIG. 10C). Here, after the insulating layer152 and the like are removed to expose at least the insulating layer104, the insulating layer 156 is formed. In the case where a pluralityof panels are formed over one substrate, the insulating layers areetched on the edge of each region in which each panel is formed, and aredivided into separate elements constituting each panel.

The insulating layer 156 serves as a barrier layer, and is preferablyformed to cover at least the integrated circuit portion 125 includingthe thin film transistor 106. Here, the integrated circuit portion 125and the first electrode 150 are surrounded by the insulating layer 104and the insulating layer 156 serving as barrier layers. As theinsulating layer 156, a nitrogen-containing layer (silicon nitride,silicon nitride oxide, silicon oxynitride, or the like) can be used.

In order that the element layer 124 including the thin film transistor106 and the like is easily separated from the substrate 100, a groove ispreferably formed by laser light irradiation before the element layer124 is separated from the substrate 100. Here, the groove 128 is formedby irradiating the insulating layers 156 and 104 on the edge of thesubstrate with laser light (see FIG. 10D).

Next, a separate film 158 is formed to cover at least the groove 128(see FIG. 11A).

Next, the first structure body 132 in which the fibrous body 132 a isimpregnated with the first organic resin 132 b is provided on thesurface of the insulating layer 156 (see FIG. 11B). Then, the firststructure body 132 is subjected to thermocompression bonding, wherebythe first organic resin 132 b of the first structure body 132 is firmlybonded to the insulating layer 156.

The first structure body 132 bonded to the insulating layer 156facilitates the separation, and further reduces the stress applied tothe element layer 124 before and after the separation and suppressesdamage to the thin film transistor 106, which results in improved yield.

In addition, the separate film 158, which is provided before the firststructure body 132 is bonded to the insulating layer 156, suppressesseparation defects in which the first organic resin 132 b enters thegroove 128 to be attached to the separation layer 102.

Next, the element layer 124 is separated from the substrate 100 at theinterface between the separation layer 102 and the insulating layer 104serving as a buffer layer (see FIG. 11C). The separation starts from thegroove 128. After the separation, the separate film 158 is removed (seeFIG. 12A).

Next, the charged particle-containing layer 134 is formed over the firstelectrode 122 (see FIG. 12B).

Next, the second structure body 142 on which the second electrode 140has been formed in advance is provided over the chargedparticle-containing layer 134 (see FIG. 13A). Here, the second electrode140 is formed on the second organic resin 142 b that is semi-cured.Then, the second structure body 142 is subjected to thermocompressionbonding while the second electrode 140 faces the chargedparticle-containing layer 134, whereby the second organic resin 142 b isbonded to the first organic resin 132 b (see FIG. 13B).

Through the above steps, the electronic paper can be manufactured.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 4

In this embodiment, a method for manufacturing a display deviceincluding a thin film transistor that is formed by a process at arelatively low temperature (lower than 500° C.) (such as a thin filmtransistor with an amorphous semiconductor film, a microcrystallinesemiconductor film, or the like, a thin film transistor with an organicsemiconductor film, or a thin film transistor with an oxidesemiconductor) will be described below.

First, the separation layer 102 is formed on a surface of the substrate100, and then the insulating layer 104 is formed (see FIG. 14A). Theseparation layer 102 and the insulating layer 104 can be formedcontinuously.

Next, a thin film transistor 304 is formed over the insulating layer 104(see FIG. 14B). In this embodiment, as the thin film transistor, aninverted staggered thin film transistor having a channel formationregion that is made of an amorphous semiconductor, a microcrystallinesemiconductor, an organic semiconductor, or an oxide semiconductor isdescribed.

The thin film transistor 304 has at least a gate electrode 306, a gateinsulating layer 308, and a semiconductor layer 310. Over thesemiconductor layer 310, impurity semiconductor layers 312 serving as asource region and a drain region may be formed. In addition, wirings 314are formed in contact with the impurity semiconductor layers 312.

The gate electrode 306 can be formed having a single-layer structure ora multi-layer structure using a metal material such as chromium, copper,neodymium, or scandium or an alloy containing any of these metalmaterials as its main component, as well as the metal given as anexample for the gate electrode 112 in the above embodiment.Alternatively, a semiconductor layer typified by polycrystalline silicondoped with an impurity element such as phosphorus or an AgPdCu alloy maybe used. Further alternatively, a conductive oxide or a composite oxidemade of indium, gallium, aluminum, zinc, tin, or the like may be used.For example, a transparent gate electrode may be formed using indium tinoxide (ITO).

The gate electrode 306 can be formed by forming a conductive layer overthe insulating layer 104 by sputtering or vacuum evaporation using theaforementioned material, forming a mask over the conductive layer byphotolithography, ink-jet, or the like, and etching the conductive layerusing the mask.

Alternatively, the gate electrode 306 can be formed by discharging aconductive nanopaste of silver, gold, copper, or the like onto thesubstrate by ink-jet and baking the conductive nanopaste. Note that inorder to improve the adhesion between the gate electrode 306 and theinsulating layer 104, a nitride layer of the aforementioned metalmaterial may be provided between the insulating layer 104 and the gateelectrode 306. Here, the gate electrode 306 is formed by forming aconductive layer over the insulating layer 104 and etching theconductive layer using a resist mask that is formed using a photomask.

Note that an end portion of the gate electrode 306 is preferably taperedin order to prevent disconnection at a portion with a difference inheight, for a semiconductor layer and wirings are formed over the gateelectrode 306 in later steps. To make the end portion of the gateelectrode 306 tapered, etching may be performed with a resist maskreceding. For example, by mixing an oxygen gas into an etching gas,etching can be performed with a resist mask receding.

In the step of forming the gate electrode 306, a gate wiring (a scanline) can also be formed at the same time. Note that a scan line refersto a wiring for selecting a pixel, and a capacitor wiring refers to awiring connected to one electrode of a storage capacitor in a pixel.Note that the present invention is not limited thereto, and one or bothof a gate wiring and a capacitor wiring may be formed separately fromthe gate electrode 306.

The gate insulating layer 308 can be formed having a single-layerstructure or a multi-layer structure using silicon oxide, siliconnitride, silicon oxynitride, silicon nitride oxide, hafnium oxide,hafnium aluminum oxide, hafnium silicon oxynitride, or yttria by CVD,sputtering, pulsed laser deposition (PLD), or the like. When the gateinsulating layer 308 is formed at a high frequency (1 GHz or more) usinga microwave plasma CVD apparatus, the dielectric strength between thegate electrode and the drain and source electrodes can be improved, sothat a highly reliable thin film transistor can be obtained.

The semiconductor layer 310 is a non-single-crystal semiconductor layerhaving a thickness of 10 nm to 200 nm, and preferably a thickness of 20nm to 150 nm. As the non-single-crystal semiconductor layer, anamorphous semiconductor layer, a microcrystalline semiconductor layer,or the like can be used. As the semiconductor, silicon, germanium, asilicon-germanium compound, or the like can be used. A feature of thisembodiment is to form the semiconductor layer 310 directly over the gateinsulating layer 308 at a low temperature lower than 500° C. withoutperforming laser light irradiation, heat treatment, or the like. Withthe use of a layer containing at least molybdenum as the separationlayer 302, a separation process can be easily carried out even when athin film transistor is formed at a low temperature lower than 500° C.

Note that the semiconductor layer 310 may have a structure in which amicrocrystalline semiconductor layer is formed in contact with the gateinsulating layer and an amorphous semiconductor layer is stackedthereover. The semiconductor layer 310 may alternatively be formed of anon-single-crystal semiconductor which contains nitrogen or an NH groupand includes crystal grains having an inverted conical or pyramidalshape and/or microcrystal grains having a grain size of 1 nm to 10 nm,preferably, 1 nm to 5 nm, in an amorphous structure.

As the semiconductor layer 310, an impurity element imparting oneconductivity type, such as phosphorus imparting n-type conductivity, maybe added to an amorphous semiconductor or a microcrystallinesemiconductor. Alternatively, as the semiconductor layer 310, a metalelement which reacts with silicon to form silicide, such as titanium,zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,tungsten, cobalt, nickel, or platinum, may be added to an amorphoussemiconductor or a microcrystalline semiconductor. By addition of animpurity element imparting one conductivity type, a metal element whichreacts with silicon to form silicide, or the like, the carrier mobilityof a semiconductor layer can be increased. Thus, the field-effectmobility of a thin film transistor having the semiconductor layer as achannel formation region can be increased.

The semiconductor layer 310 can also be made of metal oxide or anorganic semiconductor material. As typical examples of the metal oxide,there are zinc oxide and zinc—gallium—indium oxide.

The impurity semiconductor layers 312 may be formed using asemiconductor layer to which an impurity element imparting oneconductivity type is added. In the case where an n-channel thin filmtransistor is formed, phosphorus may be used as the impurity elementimparting one conductivity type; typically, the impurity semiconductorlayers 312 are made of amorphous silicon or microcrystalline siliconwhich contains phosphorus. In the case where a p-channel thin filmtransistor is formed, boron may be used as the impurity elementimparting one conductivity type; typically, the impurity semiconductorlayers 312 are made of amorphous silicon or microcrystalline siliconwhich contains boron.

When including an impurity element imparting one conductivity type,phosphorus or boron in this embodiment, at a concentration of 1×10¹⁹cm⁻³ to 1×10²¹ cm⁻³, the impurity semiconductor layers 312 can makeohmic contact with the wirings 314 and serve as a source region and adrain region.

The impurity semiconductor layers 312 each are formed to a thickness of10 nm to 100 nm, and preferably 30 nm to 50 nm.

The wirings 314 can be formed of the materials listed for the wirings118 in the above embodiment. For example, a conductive oxide or acomposite oxide made of indium, gallium, aluminum, zinc, or tin may beused for the wirings 314.

Next, an insulating layer 316 and an insulating layer 318 are formed tocover the thin film transistor 304 (see FIG. 14C). The thin filmtransistor 304 can be applied to a switching transistor of a pixel ofelectronic paper, like the thin film transistors shown in Embodiments 2and 3.

Next, an opening 321 is formed to reach the source electrode or thedrain electrode that is formed by the wiring 314. Note that when theopening 323 is formed, the insulating layer 316 and/or the insulatinglayer 318 on the edge of the substrate 100 are removed by etching or thelike. In this embodiment, it is preferable that at least the insulatinglayer 318 be removed so that the insulating layer 316 is exposed. Notethat in the case where a plurality of panels are formed over onesubstrate, it is preferable that at least the insulating layer 318 beetched on the edge of each region in which each panel is formed, anddivided into separate elements constituting each panel.

Next, a first electrode 322 functioning as a pixel electrode is providedover the insulating layers 316 and 318 to be connected to the sourceelectrode or the drain electrode through the opening 323 (see FIG. 14D).In addition, a barrier layer may be formed to cover the thin filmtransistor 304 and the first electrode 322 as illustrated in FIG. 6D.

The insulating layer 316 can be made of a material similar to that ofthe gate insulating layer 308. In addition, the insulating layer 316 ispreferably made of silicon nitride that is dense so as to prevent theentry of an impurity element which may be a contaminant, such as anorganic substance, a metal, or moisture floating in the air. Theinsulating layer 318 can be formed in a manner similar to the insulatinglayer 116 described in the above embodiment. The first electrode 322functioning as a pixel electrode can be formed in a manner similar tothe first electrode 122 shown in the above embodiment.

Before the element layer 324 is separated from the substrate 100, agroove 327 is preferably formed by laser light irradiation. Here, thegroove 327 is formed by irradiating the gate insulating layer 308 andthe insulating layer 104 exposed on the edge of the substrate with laserlight 326 (see FIG. 14E).

The subsequent steps are performed in a manner similar to thoseillustrated in FIGS. 7A to 9A, whereby the electronic paper can bemanufactured (see FIG. 15).

By applying this embodiment, the manufacturing steps can be performed ata relatively low temperature (less than 500° C.).

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 5

In this embodiment, a method for manufacturing electronic paper with asmaller number of steps will be described below. Specifically, a methodfor manufacturing electronic paper that includes a thin film transistormade of an oxide semiconductor will be described below.

First, a gate electrode 402 is formed over the first structure body 132,and a gate insulating layer 404 is formed over the gate electrode 402(see FIG. 16A). The gate electrode 402 and the gate insulating layer 404are formed of materials similar to those of the gate electrode 306 andthe gate insulating layer 308 that are shown in the above embodiment.

In this embodiment, the first structure body 132 in which the fibrousbody 132 a is impregnated with the first organic resin 132 b is used asa substrate. Note that the first organic resin 132 b may be a cured orsemi-cured organic resin.

Before the gate electrode 402 is formed over the first structure body132 that serves as a substrate, an insulating layer 400 serving as abase film may be formed between the first structure body 132 and thegate electrode 402. This insulating layer 400 prevents an impurity suchas moisture or alkali metal from diffusing into a TFT element from thefirst structure body 132 and prevents a decrease in reliability or thelike of a semiconductor element formed in an element formation layer,and may be provided as a blocking layer as appropriate.

The insulating layer 400 is made of an insulating material such assilicon oxide, silicon nitride, silicon oxynitride, or silicon nitrideoxide. For example, when the insulating layer 400 has a two-layerstructure, a silicon nitride oxide layer may be formed as the firstinsulating layer and a silicon oxynitride layer may be formed as thesecond insulating layer. Alternatively, a silicon nitride layer may beformed as the first insulating layer and a silicon oxide layer may beformed as the second insulating layer.

Next, with the use of a resist mask that is formed using a photomask, acontact hole is formed in the gate insulating layer 404 to expose aconnection pad of the gate electrode 402. At the same time, a peripheralportion is etched to form a groove 406. In the case where the insulatinglayer 400 serving as a base film is provided, the insulating layer 400as well as the gate insulating layer 404 is processed by dry etching toform the groove 406 (see FIG. 16B).

By removing the gate insulating layer and the insulating layer 400serving as a base layer in the peripheral portion, thermal fusion ofprepregs can be achieved in a later step. For dry etching, a mixed gasof CHF₃ is used; however, the present invention is not limited to thisexample.

Next, a semiconductor layer is deposited over the gate insulating layer404, and then, with the use of a resist mask that is formed using aphotomask, the semiconductor layer is etched using a dilutedhydrochloric acid or an organic acid, e.g., a citric acid, to form asemiconductor layer 408 (see FIG. 16C). Then, the photoresist is removedusing an organic solvent.

The semiconductor layer 408 is formed using an oxide semiconductorlayer. For the oxide semiconductor layer, a composite oxide of anelement selected from indium, gallium, aluminum, zinc, and tin can beused. As examples thereof, there are zinc oxide (ZnO), indium oxidecontaining zinc oxide (IZO), oxide containing indium oxide, galliumoxide, and zinc oxide (IGZO). An oxide semiconductor can be deposited asa film at a temperature lower than the upper temperature limit of aprepreg by sputtering, pulsed laser deposition (PLD), or the like andcan thus be formed directly over the prepreg.

The semiconductor layer may be formed to a thickness of 10 μm to 200 nm,and preferably 20 nm to 150 μm. It is preferable to control the oxygenconcentration in a deposition atmosphere because carrier densityincreases and characteristics of a thin film transistor degrade ifoxygen vacancies increase in a film.

In the case of using oxide containing indium oxide, gallium oxide, andzinc oxide, the semiconductor layer 408 has a high degree of freedom forthe relative proportions of the metal elements and functions as asemiconductor over a wide range of mixing ratios. Indium oxidecontaining zinc oxide of 10 wt. % (IZO), and a material in which indiumoxide, gallium oxide, and zinc oxide are mixed together in equimolaramounts (IGZO) can be given as examples.

In this embodiment, a method using IGZO is described as an example ofthe method for forming the semiconductor layer 408. A semiconductorlayer is formed by direct current (DC) sputtering at an output of 500 Wusing a target that has a diameter of 8 inches and is obtained bysintering an equimolar mixture of indium oxide (In₂O₃), gallium oxide(Ga₂O₃), and zinc oxide (ZnO). The semiconductor layer is deposited to athickness of 100 nm under conditions where the chamber pressure is 0.4Pa and the gas flow ratio of Ar/O₂ is 10/5 (sccm). It is preferable thatoxygen partial pressure during deposition be set higher than that underdeposition conditions for a transparent conductive film such as anindium tin oxide (ITO) film so that oxygen vacancies can be reduced.

Next, wirings 412 and 414 are formed over the semiconductor layer 408.The wirings 412 and 414 can be made of a material similar to that of thewirings 314 shown in the above embodiment.

The wirings 412 and 414 are formed such that part of the semiconductorlayer 408 is exposed by a lift-off method in which after a resist maskis formed over at least the semiconductor layer 408, a conductive layeris formed over the resist mask, the semiconductor layer 408, and thegate insulating layer 404 by sputtering or vacuum evaporation and thenthe resist is removed (see FIG. 16D).

Through the above steps, the thin film transistor including asemiconductor layer made of an oxide semiconductor can be manufactured.The thin film transistor of this embodiment can be applied to aswitching thin film transistor of a pixel of electronic paper, like thethin film transistors shown in the above embodiments.

After an insulating layer 418 including openings 420 and 422 is formed,a first electrode 424 functioning as a pixel electrode is provided overthe insulating layer 418 to be connected to the wiring 414 through theopening 420 (see FIG. 17A).

The insulating layer 418 can be formed in a manner similar to theinsulating layer 316 shown in the above embodiment. In the case where aninsulating layer is formed on the entire surface of the substrate, theopenings 420 and 422 can be formed by forming a resist mask byphotolithography and etching the insulating layer using the mask.Alternatively, the insulating layer 418 including the openings 420 and422 may be formed by printing or droplet discharging.

Through the above steps, the thin film transistor can be formed over theprepreg. In this embodiment, the thin film transistor can be formeddirectly over the prepreg without performing the separation process;therefore, the number of steps for forming a flexible element substratecan be reduced.

The subsequent steps are performed in a manner similar to thoseillustrated in FIGS. 8B to 9A, whereby the electronic paper can bemanufactured (see FIG. 17B).

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 6

In this embodiment, electronic paper having a structure different fromthat shown in Embodiment 1 will be described with reference to drawings.Specifically, each of a first insulating film and a second insulatingfilm that are firmly bonded to an element formation layer to seal theelement formation layer includes stacked insulating layers havingdifferent properties against external stress, so that the resistance ofthe electronic paper to external stress can be increased.

The electronic paper shown in this embodiment includes the firstinsulating film 51 and the second insulating film 52 that are shown inthe above embodiment. As the first insulating film 51, a first structurebody 71 and a first protective film 75 are stacked, and as the secondinsulating film 52, a second structure body 72 and a second protectivefilm 76 are stacked (see FIG. 2). That is, the structure illustrated inFIG. 2 corresponds to a structure in which the first protective film 75and the second protective film 76 are added to the aforementionedstructure illustrated in FIG. 1A.

The first structure body 71 and the first protective film 75 are made ofinsulators having different properties against external stress. Here,the first structure body 71 and the first protective film 75 are stackedin this order from the side of the element formation layer 53.Similarly, the second structure body 72 and the second protective film76 are stacked in this order from the side of the element formationlayer 53.

The first structure body 71 can be obtained by impregnating the fibrousbody 71 a with the first organic resin 71 b, and the second structurebody 72 can be obtained by impregnating the fibrous body 72 a with thesecond organic resin 72 b. In that case, each of the first structurebody 71 and the second structure body 72 preferably has a modulus ofelasticity of 13 GPa or more and a modulus of rupture of less than 300MPa. In this embodiment, the first structure body 71 and the secondstructure body 72 serve as an impact-resistant layer against the forceexternally applied to the element formation layer 53.

The first protective film 75 and the second protective film 76 arepreferably made of a material having a lower modulus of elasticity andhigher rupture strength than the first structure body 71 and the secondstructure body 72, and a rubber-elastic film may be used. For example,the first protective film 75 and the second protective film 76 are madeof a high-strength material such as a polyvinyl alcohol resin, apolyester resin, a polyamide resin, a polyethylene resin, an aramidresin, a polyparaphenylene benzobisoxazole resin, or a glass resin. Byusing the high-strength material having elasticity for the firstprotective film 75 and the second protective film 76, load such aslocally applied force can be evenly dispersed and absorbed, which canprevent damage to the electronic paper.

More specifically, the first protective film 75 and the secondprotective film 76 can be made of an aramid resin, a polyethyleneterephthalate (PET) resin, a polyethylene naphthalate (PEN) resin, apolyethersulfone (PES) resin, a polyphenylene sulfide (PPS) resin, apolyimide (PI) resin, or the like. Furthermore, each of the firstprotective film 75 and the second protective film 76 preferably has amodulus of elasticity of 5 GPa to 12 GPa and a modulus of rupture of 300MPa or more. In this embodiment, the first protective film 75 and thesecond protective film 76 serve as an impact-dispersing layer thatdisperses the force externally applied to the element formation layer53.

In this manner, the first structure body 71 and the second structurebody 72 each serving as an impact-resistance layer are stacked on thefirst protective film 75 and the second protective film 76 each servingas an impact-dispersing layer, respectively. Thus, the force locallyapplied to the element formation layer 53 can be reduced, which canprevent damage to the electronic paper, defects of the characteristicsof the electronic paper, and the like.

In addition, when the first insulating film 51 in which the firststructure body 71 is stacked on the first protective film 75 and thesecond insulating film 52 in which the second structure body 72 isstacked on the second protective film 76 are symmetrically disposed withrespect to the element formation layer 53, the force applied to theelement formation layer 53 when the electronic paper is curved or thelike can be evenly dispersed; therefore, damage to the element formationlayer 53 due to bending or warping of the electronic paper can bereduced.

Next, a method for manufacturing the structure illustrated in FIG. 2will be briefly described.

After the aforementioned steps illustrated in FIGS. 6A to 7B areperformed, the first structure body 132 is provided on the separationsurface of the element layer. Then, a first protective film 191 isadhered to a surface of the first organic resin 132 b before the firstorganic resin 132 b is cured. After that, the first structure body 132and the first protective film 191 are subjected to thermocompressionbonding so that the first organic resin 132 b is plasticized or cured,whereby a stack of the first structure body 132 and the first protectivefilm 191 can be obtained (see FIG. 18A).

For example, in the case where a thermosetting epoxy resin is used asthe first organic resin 132 b, the first structure body 132 is providedon the separation surface of the element layer 124 and the firstprotective film 191 is provided on the surface of the first structurebody 132, and then, thermocompression bonding is performed, whereby thefirst organic resin 132 b and the first protective film 191 can bestacked in this order on the separation surface of the element layer124. In the case where a thermoplastic resin is used, the firststructure body 132 is provided on the separation surface of the elementlayer 124 and the first protective film 191 is provided on the surfaceof the first structure body 132. Then, the first structure body 132 andthe first protective film 191 are bonded to the element layer 124 bythermocompression bonding, and then cooled to room temperature so thatthe plasticized organic resin can be cured.

The first protective film 191 can prevent the elements such astransistors from being damaged in compression bonding, which results inimproved yield.

After the aforementioned steps illustrated in FIGS. 8A and 8B areperformed, the second structure body 142 is provided on the secondelectrode 140. A second protective film 192 is adhered to the surface ofthe second organic resin 142 b before the second organic resin 142 b iscured. Then, the second structure body 142 and the second protectivefilm 192 are subjected to thermocompression bonding, whereby a stack ofthe second structure body 142 and the second protective film 192 can beobtained (see FIG. 18B).

Also in the aforementioned manufacturing steps of Embodiments 3 to 5,the protective film is adhered to the organic resin that is not curedand then the organic resin is cured, whereby a stack of the structurebody and the protective film can be manufactured.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 7

In this embodiment, electronic paper having a structure different fromthat shown in Embodiment 1 will be described with reference to drawings.Specifically, a conductive film is provided on surfaces of a firstinsulating film and a second insulating film. Accordingly, staticelectricity applied to the electronic paper by electrostatic dischargecan be diffused and discharged, whereby charges can be prevented frombeing localized (a local potential difference can be prevented).

In the electronic paper shown in this embodiment, a first conductivefilm 81 and a second conductive film 82 that are electrically connectedto each other are provided on the surfaces of the first insulating film51 and the second insulating film 52 shown in the above embodiment,respectively (see FIGS. 3A and 3B).

That is, the structure illustrated in FIG. 3A corresponds to a structurein which the first conductive film 81, the second conductive film 82,and a conductor 85 for electrically connecting the first conductive film81 and the second conductive film 82 are added to the aforementionedstructure illustrated in FIG. 1A. The structure illustrated in FIG. 3Bcorresponds to a structure in which the first conductive film 81 and thesecond conductive film 82 are added to the structure illustrated in FIG.2.

By providing the first conductive film 81 and the second conductive film82, static electricity applied by electrostatic discharge can bediffused and discharged, or localization of charges can be prevented.Thus, damage and display defects of the electronic paper due to staticelectricity can be suppressed.

The first conductive film 81 and the second conductive film 82 need tobe provided in a region overlapping at least the element formation layer53. For example, as illustrated in FIGS. 3A and 3B, the first conductivefilm 81 and the second conductive film 82 may be provided on the entiresurfaces of the first insulating film 51 and the second insulating film52, respectively. If the conductive film is provided on the entiresurface of the insulating film, a wide region can be protected againststatic electricity.

In particular, when the first conductive film 81 provided on the surfaceof the first insulating film 51 is electrically connected to the secondconductive film 82 provided on the surface of the second insulating film52, static electricity can be effectively diffused and localization ofcharges can be effectively prevented. Accordingly, it is possible tomore effectively prevent damage and display defects of the electronicpaper due to static electricity.

The first conductive film 81 can be electrically connected to the secondconductive film 82 by providing a conductor 83 on the sides of the firstinsulating film 51 and the second insulating film 52 as illustrated inFIG. 3B. In that case, the conductor 83 can be made of the same materialas the first conductive film 81 and the second conductive film 82.

Alternatively, the first conductive film 81 can be electricallyconnected to the second conductive film 82 by using the conductor 85that penetrates the first insulating film 51 and the second insulatingfilm 52 as illustrated in FIG. 3A.

Note that the conductive film may be provided on one of the surfaces ofthe first insulating film 51 and the second insulating film 52.Furthermore, even in the case where the conductive films are provided onthe surfaces of the first insulating film 51 and the second insulatingfilm 52, the first conductive film 81 and the second conductive film 82are not necessarily electrically connected to each other.

The electronic paper shown in this embodiment displays images by usingthe charged particle-containing layer 56 so that the images are seenfrom the outside. Therefore, the conductive films provided on thesurfaces of the first insulating film 51 and the second insulating film52 need to be made of a conductive material transmitting light (at leastin the visible region), as well as need to suppress damage and displaydefects of the electronic paper due to static electricity. In otherwords, the first conductive film 81 and the second conductive film 82are preferably made of a conductive material transmitting light, orformed to be thin enough to transmit light.

For example, the first conductive film 81 and the second conductive film82 can be made of indium tin oxide (ITO) in which tin oxide is mixedwith indium oxide, indium tin silicon oxide (ITSO) in which siliconoxide is mixed with indium tin oxide (ITO), indium zinc oxide (IZO) inwhich zinc oxide is mixed with indium oxide, zinc oxide (ZnO), tin oxide(SnO₂), or the like.

The first conductive film 81 and the second conductive film 82 can alsobe made of a material with a low resistivity, such as titanium oraluminum. If a material with a low resistivity is used, the sheetresistance of the first conductive film 81 and the second conductivefilm 82 can be sufficiently reduced even when they have an extremelysmall thickness. Thus, static electricity can be effectively diffusedwhile light transmittance is maintained.

The first conductive film 81 and the second conductive film 82 may alsobe made of metal, metal nitride, metal oxide, or the like other than theaforementioned titanium, aluminum, indium tin oxide, and the like, ormay have a multi-layer structure of such a conductive film.

Alternatively, the first conductive film 81 and the second conductivefilm 82 may be made of a conductive macromolecule (also referred to as aconductive polymer). As the conductive macromolecule, a so-calledπ-electron conjugated conductive polymer can be used. As the π-electronconjugated conductive polymer, for example, there are polyaniline and/ora derivative thereof, polypyrrole and/or a derivative thereof,polythiophene and/or a derivative thereof, and a copolymer of pluralkinds of those materials.

The first conductive film 81 and the second conductive film 82 can beformed by a dry process such as sputtering, plasma CVD, or evaporation,or by coating, printing, droplet discharging (ink-jet), plating, or thelike.

In the case where an integrated circuit portion includes an antenna forwireless communication with the outside, the first conductive film 81and the second conductive film 82 are made to have such a thickness thatelectromagnetic waves for communicating data with the outside passtherethrough and images can be recognized.

Next, a method for manufacturing the structure illustrated in FIG. 3Awill be briefly described.

First, as shown in the above embodiment, the first insulating film 51and the second insulating film 52 are firmly bonded to the elementformation layer 53 to seal the element formation layer 53. Then, thefirst conductive film 81 and the second conductive film 82 are formed bya dry process such as sputtering, plasma CVD, or evaporation, or bycoating, printing, droplet discharging (ink-jet), plating, or the like.Next, an opening penetrating the first insulating film 51 and the secondinsulating film 52 is formed and filled with the conductor 85, wherebythe first conductive film 81 is electrically connected to the secondconductive film 82. Note that the opening is formed in a region thatdoes not overlap the element formation layer 53.

Alternatively, an opening may be formed before the first conductive film81 and the second conductive film 82 are formed, and the firstconductive film 81, the second conductive film 82, and the conductor 85may be formed at the same time by plating. Further alternatively,instead of providing an opening, a needle-like conductor 85 may be stuckin the first insulating film 51 and the second insulating film 52 topenetrate the insulating films 51 and 52, so that the first conductivefilm 81 can be electrically connected to the second conductive film 82.

Next, a method for manufacturing the structure illustrated in FIG. 3Bwill be briefly described.

First, in FIG. 18A, the first structure body 132 is provided on theseparation surface of the element layer. Then, the first protective film191 on which a first conductive film 195 has been provided in advance isadhered to a surface of the first organic resin 132 b before the firstorganic resin 132 b is cured. After that, the first structure body 132,the first protective film 191, and the first conductive film 195 aresubjected to thermocompression bonding so that the first organic resin132 b is plasticized or cured, whereby a stack of the first structurebody 132, the first protective film 191, and the first conductive film195 can be obtained (see FIG. 19A).

Also in FIG. 18B, the second structure body 142 is provided on thesecond electrode 140. The second protective film 192 on which a secondconductive film 196 has been provided in advance is adhered to thesurface of the second organic resin 142 b before the second organicresin 142 b is cured. Then, the second structure body 142 and the secondprotective film 192 are subjected to thermocompression bonding, wherebya stack of the second structure body 142, the second protective film192, and the second conductive film 196 can be obtained.

After that, the first conductive film 195 is electrically connected tothe second conductive film 196. Here, a region that does not overlap theelement formation layer is irradiated with laser light 194 so as to meltthe first structure body 132, the second structure body 142, the firstprotective film 191, and the second protective film 192, whereby thefirst conductive film 195 is electrically connected to the secondconductive film 196 (see FIG. 19B).

In the case where plural pieces of electronic paper are formed over onesubstrate, the edge of each electronic paper is irradiated with laserlight, so that the pieces of electronic paper can be divided intoseparate electronic paper and the first conductive film 195 can beelectrically connected to the second conductive film 196 in eachelectronic paper.

When the first conductive film 195 and the second conductive film 196are electrically connected to each other to have the same potential, theeffect of protection against static electricity can be obtained. Beforethe element formation layer is charged up with static electricity to bedamaged, the electronic paper can be protected by making the top andbottom surfaces of the electronic paper have the same potential.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 8

In this embodiment, the structure shown in the above embodiment, whichis improved in adhesion between the first insulating film and the secondinsulating film, and a method for manufacturing the structure will bedescribed with reference to drawings.

The electronic paper shown in this embodiment has a structure in whichone of the first organic resin 132 b and the second organic resin 142 bhas a depressed portion in a region where the first organic resin 132 band the second organic resin 142 b are bonded to each other, so that thearea of the bonding surface is increased.

Specifically, in FIG. 9A, a depressed portion 198 is formed in the firstorganic resin 132 b of the first structure body 132 before the secondstructure body 142 is bonded (see FIG. 20A). The depressed portion 198can be formed by selectively removing part of the first organic resin132 b by laser light irradiation or the like. The depressed portion 198is formed in a region where the first organic resin 132 b and the secondorganic resin 142 b are bonded to each other.

The second organic resin 142 b is bonded to the first organic resin 132b after the depressed portion 198 is provided in the first organic resin132 b, so that the depressed portion 198 can be filled with the secondorganic resin 142 b (see FIG. 20B). As a result, the area of the bondingsurface of the first organic resin 132 b and the second organic resin142 b can be increased and the bonding strength can be increased. Notethat a plurality of depressed portions 198 may be provided.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 9

In this embodiment, module electronic paper to which an FPC is connectedwill be described with reference to FIGS. 21A and 21B. FIG. 21A is a topview of electronic paper that is manufactured by the method shown in theabove embodiments. FIG. 21B is a cross-sectional view along line a-b ofFIG. 21A.

The electronic paper illustrated in FIGS. 21A and 21B is manufactured byany of the methods shown in the above embodiments, and includes anelement formation layer 501 and a terminal portion 502. The elementformation layer 501 is firmly bonded to the first structure body 132 andthe second structure body 142 in each of which a fibrous body isimpregnated with an organic resin. The terminal portion 502 includes awiring 504 that receives a video signal, a clock signal, a start signal,a reset signal, and the like from a flexible printed circuit (FPC) 505serving as an external input terminal. Note that a printed wiring board(PWB) may be attached to the FPC 505 illustrated in FIGS. 21A and 21B.The electronic paper in this specification includes not only a main bodyof the electronic paper but also an FPC or a PWB attached to theelectronic paper.

In FIG. 21B, a through wiring 503 is formed to be electrically connectedto the wiring 504 provided in the terminal portion 502. The throughwiring 503 can be formed in such a manner that a through hole is formedin the first structure body 132 and the second structure body 142 with alaser, a drill, an awl, or the like, and the through hole is filled witha conductive resin by screen printing, ink-jet, or the like. Theconductive resin refers to a resin in which a conductive particle with agrain size of several tens of micrometers or less is dissolved orresolved in an organic resin.

As the conductive particle, for example, it is possible to use aconductive paste containing a metal element such as copper (Cu), silver(Ag), nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), tantalum(Ta), molybdenum (Mo), or titanium (Ti). As the organic resin containedin the conductive resin, at least one of organic resins that function asa binder, a solvent, a dispersing agent, and a coating material of metalparticles can be used. Typically, an organic resin such as an epoxyresin, a phenol resin, or a silicone resin can be used.

The through wiring 503 may be formed without forming the through hole inthe first structure body 132 and the second structure body 142. Forexample, the through wiring 503 can be formed in such a manner that aconductive resin is placed in a predetermined position on the firststructure body 132 or the second structure body 142; part of each of theorganic resin in the first structure body 132 and the second structurebody 142 is dissolved by reacting with an organic resin contained in theconductive resin; and metal particles contained in the conductive resinare infiltrated into the first structure body 132 and the secondstructure body 142.

The FPC 505 serving as an external input terminal is attached on thethrough wiring 503 formed in the first structure body 132 and the secondstructure body 142. Thus, the wiring 504 provided in the terminalportion 502 is electrically connected to the wiring 504 provided in theFPC 505 with the conductive particles contained in the through wiring503.

This embodiment can be implemented in appropriate combination with thestructures or manufacturing methods shown in the other embodiments ofthis specification.

Embodiment 10

The electronic paper shown in the above embodiments can be applied toelectronic apparatuses of various fields, which display information. Forexample, the electronic paper shown in the above embodiments can beapplied to e-book readers (electronic books), posters, advertisements onvehicles such as trains, or displays on various cards such as creditcards. Examples of the application of the electronic paper will bedescribed below with reference to FIGS. 22A and 22B.

FIG. 22A illustrates a poster 2601 using electronic paper. If anadvertisement is printed on paper, the advertisement is changed by hand.However, if using the electronic paper shown in the above embodiments,display of the advertisement can be changed in a short time. Inaddition, stable images can be obtained without display defects. Notethat the poster may have a configuration capable of wirelesslytransmitting and receiving data.

FIG. 22B illustrates an advertisement 2602 on a vehicle such as a train.If an advertisement is printed on paper, the advertisement is changed byhand. However, if using the electronic paper shown in the aboveembodiments, display of the advertisement can be changed in a short timewith less manpower. In addition, stable images can be obtained withoutdisplay defects. Note that the advertisement may have a configurationcapable of wirelessly transmitting and receiving data.

This application is based on Japanese Patent Application Ser. No.2008-180762 filed with Japan Patent Office on Jul. 10, 2008, the entirecontents of which are hereby incorporated by reference.

1. An electronic paper comprising: a first insulating film and a secondinsulating film facing each other; and an element formation layerprovided between the first insulating film and the second insulatingfilm, wherein the element formation layer comprises an integratedcircuit portion, a first electrode electrically connected to theintegrated circuit portion, a second electrode facing the firstelectrode, and a charged particle-containing layer provided between thefirst electrode and the second electrode; the first insulating filmcomprises a first structure body in which a first fibrous body isimpregnated with a first organic resin; the second insulating filmcomprises a second structure body in which a second fibrous body isimpregnated with a second organic resin; and the first organic resin andthe second organic resin are bonded to each other at edges of the firstinsulating film and the second insulating film.
 2. The electronic paperaccording to claim 1, wherein a conductive film is provided on at leastone of a surface of the first insulating film and a surface of thesecond insulating film.
 3. The electronic paper according to claim 1,wherein a first conductive film is provided on a surface of the firstinsulating film and a second conductive film is provided on a surface ofthe second insulating film; and the first conductive film and the secondconductive film are electrically connected to each other.
 4. Theelectronic paper according to claim 1, wherein the first insulating filmand the second insulating film are symmetrically disposed with respectto the element formation layer.
 5. The electronic paper according toclaim 1, wherein a barrier layers is provided between the integratedcircuit portion and the first insulating film, and between theintegrated circuit portion and the second insulating film.
 6. Theelectronic paper according to claim 1, wherein a depressed portion isprovided in the first organic resin or the second organic resin in aregion where the first organic resin and the second organic resin arebonded to each other.
 7. The electronic paper according to claim 1,wherein each of the first organic resin and the second organic resin isa thermosetting resin or a thermoplastic resin.
 8. The electronic paperaccording to claim 1, wherein each of the first fibrous body and thesecond fibrous body is a polyvinyl alcohol fiber, a polyester fiber, apolyamide fiber, a polyethylene fiber, an aramid fiber, apolyparaphenylene benzobisoxazole fiber, a glass fiber, or a carbonfiber.
 9. The electronic paper according to claim 1, wherein each of afirst protective film and a second protective film comprises any one ofan aramid resin, a polyethylene terephthalate resin, a polyethylenenaphthalate resin, a polyethersulfone resin, a polyphenylene sulfideresin, and a polyimide resin.
 10. The electronic paper according toclaim 1, wherein the integrated circuit portion comprises any one of athin film transistor, a non-volatile memory element, and a diode.
 11. Anelectronic paper comprising: a first insulating film and a secondinsulating film facing each other; and an element formation layerprovided between the first insulating film and the second insulatingfilm, wherein the element formation layer comprises an integratedcircuit portion, a first electrode electrically connected to theintegrated circuit portion, a second electrode facing the firstelectrode, and a charged particle-containing layer provided between thefirst electrode and the second electrode; the first insulating filmcomprises a first structure body in which a first fibrous body isimpregnated with a first organic resin, and a first protective filmhaving a modulus of elasticity lower than that of the first structurebody; the second insulating film comprises a second structure body inwhich a second fibrous body is impregnated with a second organic resin,and a second protective film having a modulus of elasticity lower thanthat of the second structure body; and the first organic resin and thesecond organic resin are bonded to each other at edges of the firstinsulating film and the second insulating film.
 12. The electronic paperaccording to claim 11, wherein a conductive film is provided on at leastone of a surface of the first insulating film and a surface of thesecond insulating film.
 13. The electronic paper according to claim 11,wherein a first conductive film is provided on a surface of the firstinsulating film and a second conductive film is provided on a surface ofthe second insulating film and the first conductive film and the secondconductive film are electrically connected to each other.
 14. Theelectronic paper according to claim 11, wherein the first insulatingfilm and the second insulating film are symmetrically disposed withrespect to the element formation layer.
 15. The electronic paperaccording to claim 11, wherein a barrier layers is provided between theintegrated circuit portion and the first insulating film, and betweenthe integrated circuit portion and the second insulating film.
 16. Theelectronic paper according to claim 11, wherein a depressed portion isprovided in the first organic resin or the second organic resin in aregion where the organic resin and the second organic resin are bondedto each other.
 17. The electronic paper according to claim 11, whereineach of the first organic resin and the second organic resin is athermosetting resin or a thermoplastic resin.
 18. The electronic paperaccording to claim 11, wherein each of the first fibrous body and thesecond fibrous body is a polyvinyl alcohol fiber, a polyester fiber, apolyamide fiber, a polyethylene fiber, an aramid fiber, apolyparaphenylene benzobisoxazole fiber, a glass fiber, or a carbonfiber.
 19. The electronic paper according to claim 11, wherein each of afirst protective film and a second protective film comprises any one ofan aramid resin, a polyethylene terephthalate resin, a polyethylenenaphthalate resin, a polyethersulfone resin, a polyphenylene sulfideresin, and a polyimide resin.
 20. The electronic paper according toclaim 11, wherein the integrated circuit portion comprises any one of athin film transistor, a non-volatile memory element, and a diode.
 21. Adisplay device comprising: a first insulating film comprising a fibrousbody and an organic resin wherein the fibrous body is impregnated withthe organic resin; an element formation layer over the first insulatingfilm, the element formation layer including: a second insulating film onthe first insulating film; a thin film transistor over the secondinsulating film; an interlayer insulating layer over the thin filmtransistor; a first electrode over the interlayer insulating film andelectrically connected to the thin film transistor; a chargedparticle-containing layer over the first electrode; a second electrodeover the charged particle containing layer; and a third insulating filmover the second electrode, the third insulating film comprising thefibrous body and the organic resin wherein the fibrous body isimpregnated with the organic resin, wherein the first insulating film isin contact with the second insulating film in a portion around theelement formation layer.
 22. The display device according to claim 21,wherein the thin film transistor is a top gate type.
 23. The displaydevice according to claim 21, wherein the thin film transistor is abottom gate type.
 24. The display device according to claim 21, whereinthe charged particle-containing layer is a microcapsule electrophoresissystem.
 25. A display device comprising: a first insulating filmcomprising a fibrous body and an organic resin wherein the fibrous bodyis impregnated with the organic resin; an element formation layer overthe first insulating film, the element formation layer including: asecond insulating film on the first insulating film; a thin filmtransistor over the second insulating film; an interlayer insulatinglayer over the thin film transistor; a first electrode over theinterlayer insulating film and electrically connected to the thin filmtransistor; a third insulating film over the first electrode and theinterlayer insulating film wherein the third insulating film is incontact with side surfaces of the interlayer insulating film and anupper surface of the second insulating film; a chargedparticle-containing layer over the first electrode; a second electrodeover the charged particle containing layer; and a fourth insulating filmover the second electrode, the third insulating film comprising thefibrous body and the organic resin wherein the fibrous body isimpregnated with the organic resin, wherein the first insulating film isin contact with the second insulating film in a portion around theelement formation layer.
 26. The display device according to claim 25,wherein the thin film transistor is a top gate type.
 27. The displaydevice according to claim 25, wherein the thin film transistor is abottom gate type.
 28. The display device according to claim 25, whereinthe charged particle-containing layer is a microcapsule electrophoresissystem.